Field of the Invention
The invention relates to a lighting device for vehicles with a plurality of components to be connected, comprising a light source, a light source carrier, an optical element and a heat sink, wherein a first component is connected by way of a fastener to a second component at a fastening point, and wherein the first component and the second component have different thermal expansion properties. Furthermore, the invention relates to a method for fastening flat components of a lighting module, which includes a light source carrier, an optical element and a heat sink as components of a light source, wherein a first component is applied with a flat side to a flat side of a second component and is brought to a fastening state at a fastening point by means of a fastener.
Description of the Background Art
From DE 10 2016 105 283 A1, a lighting device for vehicles is known, which comprises as components a light source, a printed circuit board and an optical element formed as a light guide for generating a predetermined light distribution. To fasten the light source carrier to the light guide, a holder is provided in which a portion of the holder is connected by means of a helical fastener with the light source carrier.
In the conventional art, however, a selective introduction of force thus produced leads to undesirable component stresses. If at least one of the components to be joined is formed of a plastic, there is a risk that the plastic material may relax. The concomitant plastic deformation of the plastic material leads to a delay, which leads to an undesirable change in the light range when connecting a light source carrier as the first component and an optical element as the second component. This can lead to oncoming road users being blinded, which is to be avoided for reasons of traffic safety. In particular, when a lens-shaped optical element, for example, is to be fastened directly on the light source carrier, undesired stresses can occur. This is due in particular to the different thermal conductivity coefficients of the materials of which the light source carrier and optical element are made. If the first component and the second component are connected, for example, by riveting or screwing, as a rule, a gap is created between the components to be connected.
In order to improve the heat conduction, the gap between the components facing each other can be filled with a heat-conducting layer, for example with a thermal compound. From EP 2 312 204 B1, a lighting device with a thermoadhesive layer is provided between a light source carrier and a heat sink in order to improve the transfer of heat in the direction of the heat sink and thus towards the outside environment. A disadvantage of the known lighting device is that unwanted stresses occur due to the selective introduction of force, and that a plurality of joining processes are necessary to mount the lighting device.